I thought that seeds were being preserved in dry form? Is there a benefit from freezing them rather than drying them?
I think that drying would be an easier and less expensive method. Plus, cryopreservation requires labs, equipment, scientists and electricity. But dry seeds don't need any of it. If maintained properly, we can use dry seed hundreds of years from now. But maintaining frozen seeds for that long sounds like a much tougher task to me.